The invention relates to a method of manufacturing orientated substrate plates for integrated semiconductor devices from ingot of semiconductor material of the III-V group, this method comprising at least the steps of:
(a) comprises a monocrystalline pulling nucleus of this material of the III-V group having an axis of symmetry parallel to a crystallographic axis OZ;
(b) pulling parallel to this crystallographic axis OZ and by the Czochralski method a monocrystalline ingot from this pulling nucleus;
(c) shaping the ingot to give it the shape of a cylinder whose axis coincides with the pulling axis;
(d) determining with an accuracy higher than half the degree obtained by a method using the diffraction of the X-rays the direction of two orientated crystallographic characteristic axes OU and OV of the straight section of the cylinder, these axes forming with the pulling axis OZ an orthonormal reference (OU, OV, OZ);
(e) forming on the body of the cylinder parallel to the axis OZ a major flat perpendicular to the axis OU and a minor flat perpendicular to the axis OV;
(f) forming substrate plates by cutting into pieces the ingot, the information of the differentiation of the crystallographic axes OU and OV being maintained due to the fact that during the step of cutting a major and a minor cant-wall resulting from the major and the minor flat, respectively, are formed on the substrate plates.
The invention is used in the industralization of the method of manufacturing the substrate plates for integrated circuits and other electronic or electrooptical devices of new semiconductor materials and especially semiconductor materials of the III-V group, such as indium phosphide (InP).
As is known from European Patent Applications No. 0 191 530 and No. 872300403.1, in order to obtain a substrate plate from a solid monocrystalline semiconductor material especially of the III-V group, this solid material must be formed by pulling according to Czochralski from a nucleus, whose axis is orientated along the crystallographic axis [0 0 1]; subsequently, the ingot obtained is cut into lamellae, whose crystallographic planes and axes must be known with an accuracy higher than half the degree. In fact, it is known from the publication of H. C. Gatos and M. C. Lavine in J. Electrochem. Soc. 107 (1960), p. 427, that these semiconductor materials have anisotropic properties and that the performances of the electronic or electrooptical circuits formed later on these substrates depend upon the orientation of the substrate and of the elements on the substrate.
It is known from the aforementioned Patent Applications to use as method of defining the orientations of the crystallographic planes and axis of the ingot of semiconductor material and of the substrate plates which are pulled therefrom the method of Laue by diffraction of X-rays. This method allows the derivation of the orientations of the elements of the crystallographic lattice and especially of the axes [110] and [110] from photography of the characteristic diffraction spots and of the very accurate measurement of the distances between spots. The axes are then defined in the form of flats perpendicular to these axes and parallel to the pulling axis from the ingot. During the cutting of the lamellae, these flats form cant-walls, which avoid restarting the definition of the axes, plates after plates.
However, frequently the use only of the method of Laue does not permit the differentiation between the axis [110] and the axis [110]. At is of greater importance with a view to the anisotropy of the properties of certain semiconductors and especially of the semiconductors of the III-V group that these axes are not confused. It is therefore necessary to differentiate them.
This differentiation is effected nowadays by two methods. The first method is known from European Patent Application No. 87 200 403.1 and is used exclusively with crystals, such as gallium arsenide, which have relatively to the axis [110] a characteristic diffraction spot having an intensity greatly different from that of the characteristic diffraction spot relative to the axis [110]. This first method therefore consists in using the Laue method for each of the flats shaped perpendicularly to the axes [110] and [110] to differentiate these axes by their diffraction spots and to form, for example, the flat perpendicular to the axis [110] of a surface larger than that of the flat perpendicular to the axis [110] in order to maintain this information by a cant-wall larger after cutting of the plates. This method is discussed in "La Revue Annuelle LEP 1981, p. 55-56" edited by "Service Information des Laboratoires d'Electronique et de Physique Appliquee, 3 Avenue Descartes 94450 Limeil-Brevannes, France".
However, this method cannot be used for certain semiconductor materials, such as indium phosphide, which have diffraction spots relative to the axes [110] and [110] of practically the same intensity.
It is also known, as applicable with any semiconductor material and especially to indium phosphide, to differentiate the axis [110] from the axis [110] by anisotropic etching of a (001) surface either of the ingot or of an already cut plate. For this purpose, a (001) surface is prepared either on the ingot or on a plate and a system of masks is formed in the form of strips parallel to the axes [110] and [110]. This method is described in "Journal of Crystal Growth" 58 (1982), 409-416.
However, these two methods have disadvantages; the first method is rapid and does not lengthen the industrial process due to the fact that all results appear simultaneously by the method of Laue. Thus, the definition and the differentiation of the axis are obtained by the same operation. However, this method is not useful for all types of crystals. The second method can be used for all types of crystals, but will lengthen the time required for the industrial processing of the monocrystals or of the plates due to the fact that the definition and the differentiation of the axes [110] and [110] are effected by two successive operations.